The present invention relates to tobacco materials useful for the manufacture of cigarettes, and in particular, to apparatus and processes for providing volume expansion of such tobacco materials.
Popular smoking articles, such as cigarettes, have a substantially cylindrical rod shaped structure and include a charge of smokable material such as shredded tobacco material (e.g., in cut filler form) surrounded by a paper wrapper thereby forming a so-called "tobacco rod". Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Typically, a filter element includes cellulose acetate tow circumscribed by plug wrap, and is attached to the tobacco rod using a circumscribing tipping material. It also has become desirable to perforate the tipping material and plug wrap, in order to provide dilution of drawn mainstream smoke with ambient air.
Tobacco material undergoes various processing stages prior to the time it is used as cut filler for cigarette manufacture. Oftentimes, the tobacco material is chemically and/or physically altered to modify its organoleptic, smoking and/or physical characteristics. In certain circumstances, it is desirable to process the tobacco material so as to increase the filling capacity of that material. In particular, it may be desirable to decrease the density of an aged tobacco material by expanding or puffing that material. Certain tobacco expansion processes are set forth in U.S. Pat. No. 30,693 to Fredrickson; U.S. Pat. No. 3,524,452 to Moser et al.; U.S. Pat. No. 3,683,937 to Fredrickson et al.; U.S. Pat. No. 3,771,533 to Armstrong; U.S. Pat. No. 4,235,250 to Utsch; U.S. Pat. No. 4,248,252 to Lendvay et al.; U.S. Pat. No. 4,258,729 to de la Burde et al.; U.S. Pat. No. 4,266,562 to Merritt et al.; U.S. Pat. No. 4,531,529 to White, et al.; U.S. Pat. No. 4,870,980 to Lowry; U.S. Pat. No. 5,031,644 to Kramer; U.S. Pat. No. 5,065,774 to Grubbs et al.; U.S. Pat. No. 5,076,293 to Kramer and U.S. Pat. No. 5,095,922 to Johnson et al.; which are incorporated herein by reference.
One method for volume expanding a tobacco material involves contacting that material with liquid (e.g., supercooled) carbon dioxide so as to impregnate that material with the liquid carbon dioxide, subjecting the impregnated tobacco material to conditions sufficient to convert at least a portion (e.g., a substantial amount) of the liquid carbon dioxide to solid carbon dioxide to provide a solid carbon dioxide-containing tobacco material, and subjecting the solid carbon dioxide-containing tobacco material to conditions sufficient to vaporize the solid carbon dioxide so as to expand the tobacco material. Such a method is referred to as a dry-ice expanded tobacco process or a "DIET" process. See, for example, the technologies proposed in U.S. Pat. No. 32,013 to de la Burde, et al; U.S. Pat. No. 32,014 to Sykes, et al; U.S. Pat. No. 4,202,357 to de la Burde et al; U.S. Pat. No. 4,308,876 to Rothchild; U.S. Pat. No. 4,377,173 to Rothchild; U.S. Pat. No. 4,388,932 to Merritt et al; U.S. Pat. No. 4,165,012 to Markwood; U.S. Pat. No. 4,243,056 to de la Burde et al; U.S. Pat. No. 4,250,898 to Utsch et al; U.S. Pat. No. 4,258,729 to de 1a Burde et al; U.S. Pat. No. 4,295,337 to Johnson et al; U.S. Pat. No. 4,307,735 to Snow et al; U.S. Pat. No. 4,312,369 to Mullen III et al; U.S. Pat. No. 4,333,483 to de la Burde et al and U.S. Pat. No. 4,366,825 to Banyasz; which are incorporated herein by reference.
The DIET process as conventionally employed can suffer from several deficiencies. In one regard, the solid carbon dioxide-containing tobacco material often has the form of a large frozen block or mass which is of quite high density and integrity, making such block or mass difficult to break into smaller pieces which can be handled and processed easily and efficiently in further processing steps. In another regard, the solid carbon dioxide-containing tobacco material is subjected to contact with a continuous stream of high temperature steam laden gas in a sublimator region in order to vaporize the solid carbon dioxide; and temporary interruption of introduction of solid carbon dioxide-containing tobacco material into the stream of high temperature gas can cause the tobacco material within the sublimator region to experience contact with the high temperature gas at an undesirably high temperature for a relatively long period of time, thus resulting in toasted, burned or charred tobacco material. In yet another regard, high temperatures experienced by the tobacco material in the sublimator region and during post-expansion collection, and movement of the tobacco material within the continuous steam of high temperature gas, can result in an undesirable toasting of the tobacco material as well as undesirable breakage of the tobacco material into small particles or fines.
It would be desirable to provide a process for efficiently and effectively expanding a tobacco material, and in particular, to provide expanded tobacco material using improved DIET processes and equipment.